⌽ — Reverse / Rotate last⌽Y reverses the last axis. [K] selects the axis.
⌽1 2 3 ⍝ 3 2 1
⌽[1]2 2⍴⍳4 ⍝ 2 2⍴3 4 1 2
N⌽Y rotates left by N places; negative N rotates right. Integral counts cycle modulo axis length.
1⌽'abcd' ⍝ 'bcda'
¯1⌽'abcd' ⍝ 'dabc'
A count array supplies counts for the unrotated axes. See ⊖.